8.4 Atmospheric Chemistry
Atmospheric chemistry studies chemical reactions in the atmosphere, including photochemistry, radical chemistry, and reaction kinetics.
OH Radical
OH is the "detergent of the atmosphere" - oxidizes most pollutants:
O$_3$ + h$\nu$ → O($^1$D) + O$_2$
O($^1$D) + H$_2$O → 2OH
Global mean OH: ~10⁶ molecules/cm³. Lifetime ~1 second.
Tropospheric Ozone Formation
NO$_2$ + h$\nu$ → NO + O
O + O$_2$ + M → O$_3$ + M
VOCs + NOx + sunlight → O₃ (photochemical smog)